This invention relates to an impeller for a centrifugal machine, and in particular, to an impeller having the blades thereof welded to the impeller's hub.
The manufacture and use of welded impellers in centrifugal machines, such as centrifugal compressors and pumps, has been utilized for many years. Typically, the blades of the impeller wheel have been placed over slots formed in the impeller hub, with the blade thereafter being welded to the hub at the blade-hub interface.
The shape of the blades employed in a centrifugal machine are generally contoured to achieve the best aerodynamic performance. In particular, the leading edge of the blade, that is the portion of the blade first contacting the medium flowing through the machine, is generally of a relatively small thickness when compared to the thickness of the remaining portion of the blade. Problems have sometime occurred in welding the blade to the hub, and in particular, the problems have generally been concentrated in the vicinity of the leading edge of the blade. Such problems have arisen as a result of attempts to weld a relatively thin section of the leading edge of the blade whereby, in some cases, the leading edge has been damaged or in severe cases destroyed by burning such edge during the welding process. In addition, in relatively small impellers, the flow passage defined by adjacent blades is also relatively narrow, making such passage particularly susceptible to becoming clogged by weld material. In view of the foregoing problems, it is extremely desirable to achieve a new method for manufacturing a welded impeller.
Even with relatively large size impellers, the present invention achieves a cost advantage over the prior art arrangement by reducing or eliminating the grinding step necessary to remove weld material deposited in the flow passages.